Not too many randonneurs are on 11 and 12 speed. The 4 arm Shimano would be the 9000, 9100, and 9200 Dura Ace (11 and 12S)
It looks like the separation of the two bonded halves is a failsafe mode, the crank, BB and pedal are not separated...?? I do have 9000 crank with lots of miles in all sort of condition, there are no apparent separations in the bonding. Not comfortable yet with my decision not to replace.